This invention relates to solvent cements in general and, more particularly, to solvent cements that can be dispensed in an aersosol spray from a sealed and pressurized container.
Solvent cements are used extensively to join conduits, pipes, fittings and other articles composed of thermoplastic material. The most commonly used thermoplastic materials for forming pipes etc. are polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and acrylonitrilebutadiene-styrene (ABS). Generally, solvent cement comprises a mixture of solvents and resin. The solvents dissolve the surface layers of the articles being joined such that when the objects are pressed together, the surface layers flow together. Upon evaporation of the solvents, a bond or weld is formed between the two articles. The resin fills any voids that may form between the articles. Often a primer is used before the solvent cement is applied to the articles. Usually, the primer is a blend of the same solvents that are present in the solvent cement.
Recommended practices for forming solvent welds are set forth in ASTM D-2855 for PVC to PVC welds, and in ASTM D-3138 for PVC to ABS welds. PVC and CPVC resin requirements are set forth in ASTM D-1784. Solvent cements are covered in ASTM 2564 for PVC, and in ASTM D-3138 for PVC to ABS. All these ASTM references are incorporated herein by reference and made a part hereof.
Conventionally, the solvent cement is stored in a container having a closable opening and is applied to the articles by a brush or rag. This method of application is messy and requires cleaning of the brush or rag. Moreover, the composition of the solvent cement often changes with repeated use due to the evaporation of the solvents from the container. In order to address the foregoing drawbacks of the conventional storage and application of solvent cement, it has been proposed to dispense solvent cement in an aerosol spray from a sealed and pressurized container. Conventional solvent cement compositions, however, tend to become unstable when stored and dispensed in this manner.
Based upon the foregoing, there is a need in the art for a solvent cement composition that can be dispensed in an aersosol spray from a sealed and pressurized container, without loss of stability. The present invention is directed to such an aerosol solvent cement composition.
In accordance with the present invention, a pressurized aerosol solvent cement product is provided having a container that includes a can, a valve cup with a valve assembly, a dip tube and an actuator. The can is comprised of tin-plated steel. An aerosol solvent cement composition is disposed within the container. The aerosol solvent cement composition includes at least 10 weight percent tetrahydrofuran, at least 10 weight percent acetone, a thermoplastic resin, a propellant selected from the group consisting of ethers, C1-C4 saturated hydrocarbons, hydrofluorocarbons, and mixtures of the foregoing, and a stabilizing composition effective to keep the solvent weld composition stable after the aerosol solvent cement product has been held at a temperature of 120xc2x0 F. for 90 days.
In accordance with another embodiment of the present invention, a pressurized aerosol solvent cement product is provided having a container that includes a can, a valve cup with a valve assembly, a dip tube and an actuator. An aerosol solvent cement composition is disposed within the container. The aerosol solvent cement composition includes a solvent system comprising at least 10 weight percent tetrahydrofuran, a thermoplastic resin, a propellant selected from the group consisting of ethers, C1-C4 saturated hydrocarbons, hydrofluorocarbons, and mixtures of the foregoing, and a stabilizing composition comprising an oxazolidine compound.
Also provided in accordance with the present invention is a method of joining two objects composed of thermoplastic. In accordance with the method, a pressurized aerosol solvent cement product is provided. The aerosol solvent cement product has a container including a can, a valve cup with a valve assembly, a dip tube and an actuator. The can is comprised of tin-plated steel. An aerosol solvent cement composition is disposed within the container. The aerosol solvent cement composition includes at least 10 weight percent tetrahydrofuran, at least 10 weight percent acetone, a thermoplastic resin, a propellant selected from the group consisting of ethers, C1-C4 saturated hydrocarbons, hydrofluorocarbons, and mixtures of the foregoing, and a stabilizing composition effective to keep the aerosol solvent cement composition stable after the aerosol solvent cement product has been held at a temperature of 120xc2x0 F. for 90 days. The actuator of the container is manipulated to cause a spray of the aerosol solvent cement composition to be ejected from the container. The spray is directed to deposit films of the aerosol solvent cement on portions of the objects to be joined. The objects are then moved to bring the portions with the aerosol solvent cement deposited thereon into contact with each other.